Vettel had built up a dominant lead in the first half of the race, but saw a gap over 20 seconds wiped out by a safety car period. On the restart Vettel got away well but then saw the field stream past him as his car coasted to a halt at turn 17. Horner speculated that an alternator problem could have been the cause - similar to that suffered by Romain Grosjean's Renault-powered Lotus - but said Vettel had "driven immaculately" until that point.

"It's just another demonstration that sometimes motor racing can be cruel," Horner told Sky Sports. "Sebastian had done everything right, he was a pit stop ahead, he'd driven immaculately, had great pace, the race was his really. Cruel, cruel luck, but we must take heart that we had a very fast car here ... bitterly disappointing for Seb but he'll be back.

"It's a suspected alternator. We need to get the car back and have a look at all the data but it looks like a similar issue to perhaps what happened on the Lotus. But we need to get it back and have a proper post mortem, but that's what we suspect. It's hard to decipher at this point exactly what the cause is so we'll get it back and we'll investigate with Renault and try and learn from it."

Vettel explained the failure caught him by surprise but tried to focus on how quick the car had been until that point.

"On the straight down to turn 17 I had to give way to the other people, the engine stalled and switched off and there was nothing we could have done," he said. "At the moment it's not clear exactly what the problem was, maybe a bit similar to the problem Mark had on Friday.

"The safety car was obviously not ideal for us and it might be that the retirement is in some regards also down to the safety car. It's a shame.

"It's s**t but we can't change it now. I think up to that point it was clear that we were very strong. I was very happy, I felt happy in the car, we had the pace and we were very, very quick today. I was surprised. I felt really good, also after the safety car the initial restart was OK, it was fine."